This invention relates to the field of laser aided land surveying instruments and methods as applied to the precise azimuth disposition of a subterranean pipe/conduit/tunnel or similar object in the earth.
Laser inclusive instruments are often used to establish the azimuth and grade for man made surface objects such as roads and buildings. Under certain conditions such instruments are also usable for accurately laying pipe and conduit in the earth and for tunneling and other below grade construction tasks. With such instruments the azimuth alignment of a pipe/conduit/tunnel can be accurately controlled with minimized expenditure of measurement and earth movement assets. In the pipe/conduit/tunnel azimuth alignment instance these instruments generally consist of a visible spectrum energy-emitting laser physically oriented by instrument azimuth and pitch-determining elements and mounted in a housing appropriate for field usexe2x80x94use at the bottom of a hole or trench for example. In such instruments azimuth or azimuth and elevation pointing of the instrument may be achieved with steering optics that also expand and collimate the laser beam.
According to present-day typical practices, after disposing a subterranean course alignment instrument at the bottom of an appropriate hole in the earth or at the bottom of an initially commenced trench, the instrument is brought to designating the desired pipe/conduit/tunnel azimuth by locating a transit or similar device on the earth surface directly above the instrument and aiming the transit at a surveying reference, e.g. a stake in the ground or a positioned surveyor""s rod, identifying the desired pipe/conduit/tunnel course. While maintaining the transit""s azimuthal alignment, the transit telescope is then pointed downward into a hole in the earth or into a commenced trench, toward a wall surface. The laser alignment instrument beam is then aimed at the same wall surface and brought into the desired alignment with a point determined by using the transit telescope reticule.
Moreover according to current practice, the transit or similar device can alternatively be used to position an alignment target on the wall within the hole or commenced trench and then bringing the laser into the desired alignment with the target. Present day subterranean course alignment instruments typically include apparatus enabling remote control of the azimuth and elevation pointing of the laser beam upon command from an operator person. A single person, using such remote aim-point control of the instrument, can usually accomplish an initial setup of an instrument in 10 to 15 minutes after excavating the trench and placing the instrument at the bottom. Subsequent realignment requires a comparable length of time. Work site equipment movement and the associated vibration however often require the instrument to be realigned frequently. The thus-described conventional alignment technique therefore requires an extensive open trench in the earth; this requirement is often considered a safety concern for people and equipment. A faster alignment capability not requiring an open trench is therefore highly desirable. The present invention addresses this need.
The present invention provides an improved subterranean course alignment laser instrument and a system for rapid and convenient calibration or setup of this instrument to obtain accurate definition of a sub surface course for a pipe/conduit/tunnel or the like. Instrument setup is made in response to an above-ground course definition marker such as a surveyor""s stake or surveyor""s rod, without use of a surveyor""s transit and while the instrument is disposed in a subterranean location. Optical elements selected in recognition of a limited error budget available in such equipment are added to the instrument to provide separate output beams for setup and for pipe/conduit/tunnel alignment uses.
It is an object of the present invention therefore to provide a subterranean course alignment instrument capable of convenient, fast and accurate setup.
It is another object of the invention to provide a subterranean course alignment instrument having single person setup capability.
It is another object of the invention to provide a subterranean course alignment instrument having desirable accuracy characteristics.
It is another object of the invention to provide a subterranean course alignment instrument capable of desirable accuracy operation under field use conditions.
It is another object of the invention to provide a subterranean course alignment instrument capable of operation within a desirably small error budget.
It is another object of the invention to provide a subterranean course alignment instrument having a two beam initial alignment procedure.
It is another object of the invention to provide a laser alignment instrument employing curved three dimensional optical elements in its initial alignment procedure.
It is another object of the invention to provide a subterranean course alignment instrument having above ground initial alignment input capability.
It is another object of the invention to provide a subterranean course alignment instrument having a pseudo periscope underground to above ground optical communication arrangement.
It is another object of the invention to provide a subterranean course alignment instrument in which complementary optical elements are used to reduce setup error characteristics.
It is another object of the invention to consider the error sources encountered in a concave beveled mirror and convex beveled mirror arrangement of a subterranean course alignment instrument.
These and other objects of the invention are achieved by a surface-referenced pipe/conduit/tunnel subterranean azimuth course-determining laser apparatus comprising the combination of:
a first laser element disposed in a subterranean receptacle and generating subterranean receptacle-contained horizontally directed radiant energy emission at an output port thereof;
a desired pipe/conduit/tunnel azimuth course marker element disposed at a surface reference location distal of said subterranean receptacle;
first curved mirror apparatus selectively coupled to said output port of said first laser element and selectively directing said subterranean receptacle-contained horizontally directed radiant energy emission upward and out of said subterranean receptacle;
second curved mirror apparatus disposed above said subterranean receptacle and said first laser element and orienting said upward and out-directed first laser element radiant energy parallel with said first laser element horizontally directed radiant energy emission away from said subterranean receptacle in an above ground selected azimuth direction toward said desired pipe/conduit/tunnel course marker element;
said subterranean receptacle-contained first laser element horizontally directed radiant energy emission selectively designating a desired subterranean azimuth course for said pipe/conduit/tunnel in response to prior optimized receipt of said first laser radiant energy at said desired pipe/conduit/tunnel course marker surface reference element via said first curved mirror apparatus and said second curved mirror apparatus.